Trim last two lines of an attributed string - ios

Question

How do I remove the last two lines of this NSAttributedString?
NSString *exampleString = #"line 1\nline 2\nline 3\nline 4"
NSAttributedString *as = [NSAttributedString alloc] int];
[as setString:exampleString];
[self removeLastTwoLinesOfAttributedString:as];
NSLog(#"%#",as);
-(void)removeLastTwoLinesOfAttributedString:(NSAttributedString *)string {
//some code here
}
I'd like to end up with #"line 1\nline 2" in this example. Thanks

Answer 1

You could do something like this :
-(NSAttributedString *) removeLastTwoLinesOfAttributedString:(NSAttributedString *aString) {
NSRange range = [aString.string rangeOfString:#"\n" options:NSBackwardsSearch];
range = [aString.string rangeOfString:#"\n" options:NSBackwardsSearch range:NSMakeRange(0, range.location)];
return [aString attributedSubstringFromRange:NSMakeRange(0, range.location)];
}
int main (int argc, const char * argv[])
{
NSString *exampleString = #"line 1\nline 2\nline 3\nline 4";
NSAttributedString *as = [[NSAttributedString alloc] initWithString:exampleString];
as = [self removeLastTwoLinesOfAttributedString:as];
NSLog(#"%#",as);
return 0;
}
Output
line 1
line 2

Answer 2

I would suggest as the best solution:
-(NSAttributedString *)removeLastTwoLinesOfAttributedString:(NSAttributedString *)aString {
if (aString.length == 0) {
return aString
}
NSString *string = [aString string];
unsigned numberOfLines, index, stringLength = [string length];
NSRange rangeOfLastTwoLines = NSMakeRange(aString.length - 1, 0);
for (index = stringLength-1, numberOfLines = 0; index >= 0 && numberOfLines < 2; numberOfLines++) {
NSRange rangeOfLine = [string lineRangeForRange:NSMakeRange(index, 0)];
rangeOfLastTwoLines = NSUnionRange(rangeOfLastTwoLines, rangeOfLine);
index -= rangeOfLine.length;
}
return [aString attributedSubstringFromRange:NSMakeRange(0, rangeOfLastTwoLines.location)];
}
This has the benefit of working with any newline character not just "\n" and it uses the preferred by Apple method for detecting lines see this
Also it will not break if the last two lines are less than 2

Answer 3

If you're using Swift you can do this, if you're using Objective-C you should look at the other answers.
You can drop the last two lines of a String like this
string.components(separatedBy: "\n").dropLast(2).joined(separator: "\n")
To do it to an attributed string just access the string property, remove the last two lines, and create an attributed string with the trimmed string and all the same attributes.